Check your firewall? Telnet from an outside computer and see if port 25 is responding?

Some home ISPs block port 25 for inbound...

 

You need a business class internet connection with 25 fully open.

I have the same issue
* Telnet port 25 shows no connection - even on the local machine
* The firewall has port 25 enabled
* Ports 23, 110, 587... all there

* I guess in our case I can weed out firewall

* Server has SMTP 25 enabled, we even have a port 25 on the IP address of the mail server in IIS
Found about 50 or so similar questions in various boards - usually the Firewall was the issue - still unclear what we can do.

 

* Just filed a ticket but really puzzled 

There are TWO independent port settings in SmarterMail 12

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We just found at least our solution: Under SETTINGS | BINDINGS | IP ADDRESSES (not PORTS) is yet another switch to turn ports on or off. When you click on the IP address you find ports to turn on or off. i.e. Port 25 was not checked in our case. It took us two days to figure that out. :(((( But now its all good.

Rob